苦苈胶压裂液研究:水溶液黏度特性

Study on Kuli Gum Fracturing Fluid:Viscosity Properties of Aqueous Kuli Gum Solution

苦苈胶是一种新的水基压裂液增稠剂,其红外光谱与瓜尔胶相同,化学成分应为半乳甘露聚糖。以瓜尔胶为对比剂考察了商品苦苈胶水溶液的黏度特性。与工业特级、一级瓜尔胶相比,同浓度的苦苈胶溶液的表面张力略高,即界面活性很弱;表现黏度（25℃）较高,温度升高时表观黏度的降幅较小,即增黏性和耐温度较好（0.4%溶液的表观黏度,20℃、90℃时分别为51.1和35.4 mPa.s）;在宽pH范围内（3.8-10.9）0.4%溶液的表观黏度与pH值间的关系相似,即表观黏度（25℃）在弱酸性和中性条件下较高,在使用压裂液的弱碱性条件下较低。以氯化物形式加入的金属阳离子浓度增大时,3种商品植物胶水溶液表观黏度（25℃）降低的趋势大体相同,降幅有所差别：Na＋（0-20 g/L）、Ca2＋（0-8 g/L）、K＋（0-41.9 g/L）、F3＋（0-5 g/L）引起的黏度下降分别为轻微、较小、较大、很大;0.4%苦苈胶溶液的黏度（25℃）在K＋浓度增至31.4和41.9 g/L时下降9%和11%,在Fe3＋浓度增至1.5 g/L时下降11%,Fe3＋对瓜尔胶溶液黏度的影响更大。

Kuli gum（KG）,a novel thickener for aqueous fracturing fluid,was identified chemically by similarity of IR spectra to guar gum to be a galactomannan.The viscosity properties of aqueous solution of commercial KG were investigated with guar gum（GG） as control.In comparison with extra and first grade commercial GG,KG solution of equal concentration had higher surface tension,or weaker interfacial activity,higher apparent viscosity at 25℃ and smaller decrement of apparent viscosity at elevated temperatures,or higher viscosifying capability and temperature resistance（the apparent viscosity of 0.4% solution was of 51.1 mPa·s at 20 ℃ and 35.4 mPa·s at 90℃）;for 0.4% solutions of these 3 plant gum at pH value in wide range 3.8—10.9,similar apparent viscosity vz pH value relationships were observed,in that the apparent viscosity at 25℃ was higher in weakly acidic and neutral media and lower in weakly alkaline media,the laters were common for a fracturing fluid.The apparent viscosity at 25℃ of 0.4% solutions of these 3 plant gum decreased in similar manners with increasing concentration of metal cations added as chlorides：Na＋ of concentration 0—20 g/L,Ca2＋of concentration 0—8 g/L,K＋ of concentration 0—41.9 g/L,and Fe3＋ of concentration 0—5 g/L caused very slight,not significant,significant,and severe decrease of apparent viscosity at 25℃,respectively;the apparent viscosity at 25% of 0.4% KG solution decreased by 9% and 11% when K＋ concentration increased to 31.4 and 41.9 g/L,respectively,and by 11% when Fe3＋ concentration increased to 1.5 g/L while Fe3＋ exerted much more negative influence on GG solution viscosity.